Police have said they need help from the public to identify victims of trafficking - after revealing they discovered one family in a field drinking rainwater from a rusty can to survive.

Derbyshire Police have issued a list of tell-tale signs of trafficking victims and asked the public to help spot them.

They say "modern slaves" have been found working in prostitution, nail bars, car washes and the building trade - but officers say it could be any area of work.

Police say they have dealt with nearly 300 reports of suspected human trafficking in the last few months in Derbyshire - including one family which was discovered cowering under tarpaulin in a Derbyshire field.

Detective Constable Andy Hulland said the family had been trafficked twice.

He told the Derby Telegraph : "We got a call from a member of the public to say they were concerned about people in a field in Derbyshire who were living under a tarpaulin.

"We got there and established they had no money. They were collecting rain water in a rusty can to drink. They spoke no English and that's the situation they dealt with.

"We established that they had been trafficked twice in the UK and had just been dumped. We have worked with other agencies to get them some food and somewhere secure to live in the county. It's all about identifying the victims and then getting them the help and support they need.

"These are the abhorrent crimes we're coming across. They are preying on the weak all of the time."

Detective Inspector Paul Tatlow

Police say trafficking victims can be refugees in the country illegally, and therefore reluctant or unable to approach authorities for help when exploit. They could also be people who come here for legitimate work, but then lose that job and fall on hard times, becoming susceptible to criminal.

Or they could even be people born here who become vulnerable when they suffer a life crisis. Traffickers keep a hold on their victims by threatening to tell authorities if a person is here illegally, or even taking away their passports or documentation.

They also use physical or mental violence to intimidate workers into doing what they want, often paying them a pittance and forcing them to live in squalid and cramped conditions.

Detective Sergeant Gareth Smethem said the force needed the help of the public. He said: "This is a crime which the public can really be on board with us on. When you go to a car wash, have a look at the demeanour and attitude of the people there.

"I want to be clear not all car washes are going to be like this. But some will. If you see people looking down, tired and scared, that could be a sign. Please let us know.

"They may look withdrawn or scruffy. If there's something there that does not seem right, then please tell us.

"If you have work done at your house and an English-speaking man arrives but the work is being carried out by reserved foreign nationals who speak little English, that is a warning sign - especially if the English speaking man comes and collects the money at the end. If you see anything suspicious, please let us know."

Detective Sergeant Smethem is part of a new Derbyshire unit - Operation Wilberforce - established by the force to find the true scale of the problem. Wilberforce officers say they "have their eyes open", but have "no idea" of the true scale of the problem they face.

The team was formed in March and Detective Chief Inspector Paul Tatlow, who oversees the operation, said it had been contacted 296 times since then by people concerned that human trafficking and modern-day slavery was taking place.

Mr Tatlow said: "Our ultimate goal is to stop people from being exploited. We want to get people out of the vicious cycle they find themselves in.

"Some of them do not know they are being exploited. There are people that are in these relationships and they do know they are victims, but what they are involved in is better than back in their own country.

"They are caught between the devil and the deep blue sea. Which is better? This can affect all parts of society."

One of the challenge they face is that not all victims see themselves as such.

Mr Tatlow added: "It's very complex. Although the fact we've had 296 people get in contact it is still vastly under-reported.

"One thing that's important to get across is this is not always nail bars and car washes. It could be farmers getting someone in to help and not paying them what they should and not treating them right.

"We used to associate slavery with something happening hundreds of years ago on ships. It's very different now."

If anyone has concerns about human trafficking, they should call police on 101.